Skin color is primarily determined by the amount and type of melanin, a brown pigment present in the skin. Lower amounts of melanin result in lighter skin color while higher amounts result in darker skin color. Also, hyper-pigmentation in the skin is caused by the over expression or accumulation of melanin in the skin. As a result, the pathway involved in melanin production has been the target for many inhibitors so as to reduce the levels produced. One of the principal enzymes involved in the melanin pathway is tyrosinase.
The synthesis of melanin is a process under hormonal control, including the melanocyte stimulating hormone (MSH) and adrenocorticotropic hormone (ACTH) peptides that are produced from the precursor proopiomelanocortin. It is stimulated by the DNA damages that are caused by UVB-radiations as well.
Then, exposure to the sun over time can induce many biochemical reactions in the skin, leading to sunburn and tanning, for example. Other consequences of exposure to the sun accumulate over time. These changes can result in the development of age spots and create an uneven, mottled skin tone. Unfortunately, many of the commercially available products in today's market are either only marginally effective, or contain active agents that are unstable and lose their potency when incorporated into a final formula.
The ability to modify the expression of pigment content in the skin, to promote an evenness skin tone or lightening skin tone, is highly desired in today's society. Many people desire to modify their skin tone, to reduce aging spots, etc., or for purely cosmetic reasons.
As a result, efforts to develop effective compositions have focused on agents that inhibit the activity of tyrosinase. For example, a variety of tyrosinase inhibitors, such as hydroquinone, vitamin C, cystein, kojic acid, arbutin and glutathione among others have been proposed in topical compositions. Also, a variety of dermatological compositions have been suggested for improving the appearance of pigment disorders such as that observed in melasma, freckles, vitiligo, piebaldism, phenylketonuria, and the like, and/or for cosmetic purposes.
Also, the use of skin bleaching compositions is widely expanded. However, they either destroy melanin or inhibit its formation. Many of these contain harsh chemicals such as peroxides, acids or formaldehyde, or thiolated materials. Less stringent therapies have other disadvantages.
Topical retinoids and topical corticosteroids have been suggested as hypo-pigmenting agents, as have laser treatment and chemical peels, but these fall short of desirable responses.
Other compositions suggested the use on the skin of natural materials, which have in some cases been used for centuries in Asia or Europe to bleach skin and skin areas, or enhance the appearance of fair skin. These include the use of lemon, orange, cucumber, ginko, carob, rose fruit, geraniuim herb, cinnamon, sweet marjoram, rosemary, etc. . . .
In order to combat disorders related to abnormal pigment or to lighten skin tone, various compounds which, when applied topically to the skin, are capable of reducing tyrosinase activity and consequently limiting melanin production, have thus been proposed. Unfortunately, the treatments currently available are not entirely satisfactory, in particular in terms of the side effects which are frequently associated therewith, such as irritant side effects with certain topical agents.
It would thus be highly desirable to have alternative preparations that do not have the drawbacks of those described in the prior art. In particular, it would be highly desirable to develop nutritional cosmetic compositions to be administered via oral route that have improved stability and efficacy to promote an evenness skin tone or to lighten skin tone.
There also remains a need to active agents that are effective for treating and/or preventing skin pigmentation disorders, in particular those due to environmental factors or aging.
The object of the present invention is to meet these needs.